For the second time in just 12 months, scientists have recorded severe coral bleaching across huge tracts of the Great Barrier Reef after completing aerial surveys along its entire length. In 2016, bleaching was most severe in the northern third of the Reef, while one year on, the middle third has experienced the most intense coral bleaching. This year there is mass bleaching, even without the assistance of El Niño conditions. [Source: ARC Centre of Excellence for Coral Reef Studies]